Ultrasound catheter and method for imaging and hemodynamic monitoring

ABSTRACT

A catheter apparatus for monitoring cardiovascular function is provided. The catheter apparatus contains an elongated body having proximal and distal ends; a phased-array ultrasonic transducer; and an electrical conductor. The phased-array ultrasonic transducer is mounted proximate the distal end of the catheter body to transmit ultrasound and receive resultant echoes so as to provide a field of view within which flow rates can be measured and features imaged. The electrical conductor is disposed in the catheter body for electrically connecting the transducer to control circuitry external of the catheter.

This is a File Wrapper Continuation application of application Ser. No.08/305,138, filed Sep. 13, 1994 and now abandoned, entitled ULTRASOUNDCATHETER AND METHOD FOR IMAGING AND HEMODYNAMIC MONITORING, which is acontinuation of patent application Ser. No. 07/972,626, filed on Nov. 6,1992, entitled TRANSVASCULAR ULTRASOUND HEMODYNAMIC AND INTERVENTIONALCATHETER AND METHOD and issued as U.S. Pat. No. 5,345,940, which is acontinuation-in-part application of Ser. No. 07/790,580, filed on Nov.8, 1991, entitled ULTRASOUND AND INTERVENTIONAL CATHETER AND METHOD andissued as U.S. Pat. No. 5,325,860.

BACKGROUND OF THE INVENTION

The present invention relates to an ultrasonic and interventionalcatheter and method. More particularly, the present invention relates tosuch a catheter which provides imaging and hemodynamic capability.Further, the invention relates to such a catheter which providestransvascular and intracardiac imaging.

Current x-ray fluoroscopy can localize radio paque devices within thecardiovascular system and outline silhouetted anatomy. Preciselocalization of intracardiac anatomy is not possible; e.g., directing acatheter predictably and repetitively through the same precise pointwithin the heart.

Ultrasound (echocardiography) can be utilized to image detailed cardiac,intracardiac, and vascular anatomy. Additionally, function,hemodynamics, and visualization of blood flow is possible. Dopplerechocardiography, which utilizes the physics of ultrasound frequency todetermine velocity and direction of blood flow, is used to determinepressure and flow and visualize blood movement within the cardiacchambers.

Ultrasound is increasingly utilized as a substitute for cardiaccatheterization.

Currently, many interventional procedures can be performed through acatheter; e.g., balloon dilation and valvuloplasty and ablation ofabnormal cardiac tissue are two frequently performed procedures.

Ultrasound has recently entered into invasive applications.Transesophageal echocardiography is the most widely utilized invasiveultrasound technique. Intravascular ultrasound utilizing miniaturetransducers mounted on a catheter are now undergoing vigorous clinicaltrials. Intracardiac imaging devices have received very limitedinvestigation.

Increasingly, therapeutic cardiac catheterization is displacingdiagnostic cardiac catheterization. Thus, there is an acceptance ofcatheter technology as a means of altering cardiac anatomy or conductionsystem. Balloon angioplasty, utilization of defect closure devices, andelectrical interruption of anomalous conduction pathways are nowconsidered accepted practice. However, most of these procedures arerather gross in nature; e.g. a large balloon splitting an obstructedvalve, crude devices inserted into defects, and application of thermalor electric energy to interrupt the conduction system or produce defectsin septa.

SUMMARY OF THE INVENTION

The present invention relates to an ultrasonic and interventionalcatheter. The present invention more particularly relates to anultrasonic and interventional catheter which provides imaging andhemodynamics, blood pressure and flow, capability. Further, theinvention relates to such a catheter which images through the vascularsystem, i.e., transvascular and intracardiac.

In one embodiment, the present invention relates to a catheter apparatuscomprising an elongated flexible body having proximal and distal endswith an ultrasonic transducer mounted proximate the distal end of thecatheter body to transmit ultrasound and receive resulting echoes so asto provide a field of view within which flow rates can be measured andfeatures imaged. An electrical conductor is disposed within the catheterbody for electrically connecting the transducer to control circuitryexternal of the catheter. A port means is disposed in the catheter bodyand extends from proximate the proximal end of the catheter body toproximate the distal end of the catheter body for receiving atherapeutic device whereby a therapeutic device can be delivered toproximate the distal end of the catheter for operation within theultrasonic transducer field of view. A guide wire port means is furtherdisposed in the catheter body and extends from proximate the proximalend of the catheter body to proximate the distal end of the catheterbody for receiving a guide wire.

The present invention further relates to a medical system comprising acatheter, control circuitry means for controlling operation of anultrasonic transducer disposed on the catheter and display means fordisplaying flow rates and features imaged by the ultrasonic transducer.In one embodiment of this invention, the catheter comprises an elongatedflexible body having proximal and distal ends. The ultrasonic transduceris mounted proximate the distal end of the catheter body to transmitultrasound and receive resultant echoes so as to provide a field of viewwithin which flow rates can be measured and features imaged. Anelectrical conductor is disposed in the catheter body for electricallyconnecting the transducer to control circuitry external of the catheter.Port means is further disposed in the catheter body and extends fromproximate the proximal end of the catheter body to proximate the distalend of the catheter body for receiving a therapeutic device whereby thetherapeutic device can be delivered to proximate the distal end of thecatheter for operation within the ultrasonic transducer field of view. Aguide wire port means is further disposed in the catheter body andextends from proximate the proximal end of the catheter body toproximate the distal end of the catheter body for receiving a guidewire.

The present invention also relates to a method of therapeuticintervention in a living body. The method includes the steps ofinserting a catheter into the body, the catheter having a body withproximal and distal ends. A surgical device is inserted into the bodythrough a port disposed in the catheter body and extending fromproximate the proximal end of the catheter body to the distal end of thecatheter body. An ultrasonic transducer disposed proximate the distalend of the catheter body is pulsed to transmit ultrasound and receiveresultant echoes. The surgical device is operated within a field of viewprovided by the ultrasonic transducer. The resultant echoes areprocessed to image the operation of the surgical device.

In some embodiments, a small (longitudinal), transverse, biplane, ormultiplane phased array ultrasound transducer is combined with acatheter delivery system. It is appreciated that this systemincorporates not only tomographic, but also other types of ultrasoundenvironments, which can be used for underblood intervention within afield of ultrasound, especially in the cardiac chambers, through vesselwalls, and within large vessels, etc. In a preferred embodiment, thedevice incorporates a 5 to 10 MHz phased array transducer with a (8French conduit) delivery port. The delivery port serves as a means todeliver other catheters (i.e., ablation catheters, etc.), recordpressure and sample blood. Within the core of the ultrasound catheterthere is also a 0.035 inch port for wire insertion. The completedcatheter device typically might require an 18 to 24 French sheath forvenous entry.

The present invention might have numerous applications. One initialapplication might be the ablation of right heart conduction tracts. Theproposed device would be ideal for ablation of right heart bypasstracts. The tricuspid valve and its annulus could be confidently mappedby direct ultrasound visualization. An electrophysiologic catheter orablation catheter could be passed through the port contained in thecatheter. The catheter could be manipulated to its destination by use ofa deflection wire disposed in the guide wire port. Precise mapping andintervention can then be carried out under direct ultrasoundvisualization.

Other applications include ultrasound guided myocardial biopsy, surgicalimplantation and/or removal of devices under ultrasound control, andtransvascular diagnosis of perivascular and organ pathology.

The present invention provides an intravascular ultrasound cathetercapable of catheter-based intervention while under visual observation.Avoidance of major surgical procedures in conjunction with precisioncatheter intervention is a substantial improvement over present patientcare.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages and objects obtained byits use, reference should be made to the drawings which form a furtherpart hereof, and to the accompanying descriptive matter, in which thereis illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the construction and operationalcharacteristics of a preferred embodiment(s) can be realized from areading of the following detailed description, especially in light ofthe accompanying drawings in which like reference numerals in theseveral views generally refer to corresponding parts.

FIG. 1 is a partial perspective view of an embodiment of a catheter inaccordance with the principles of the present invention;

FIG. 2 is an enlarged cross-sectional view taken proximate the distalend of the catheter shown in FIG. 1;

FIG. 3 is a block diagram in part and sectional diagram in partillustrating an embodiment of a system utilizing the catheter shown inFIG. 1;

FIG. 4A is an illustration illustrating an application of a catheter inaccordance with the principles of the present invention;

FIG. 4B is a partially enlarged illustration of the catheter shown inFIG. 4A.

FIG. 5A shows a partial perspective and cross-sectional view of a firstalternate embodiment of a catheter in accordance with the principles ofthe present invention;

FIG. 5B shows a view of the distal end of the embodiment of the cathetershown in FIG. 5A;

FIG. 6A shows a partial perspective and cross-sectional view of a secondalternate embodiment of a catheter in accordance with the principles ofthe present invention;

FIG. 6B shows a view of the distal end of the catheter shown in FIG. 6A;

FIG. 7A shows a partial perspective and cross-sectional view of avariation of the second alternate embodiment of the catheter shown inFIG. 6A;

FIG. 7B shows a view of the distal end of the embodiment of the cathetershown in FIG. 7A;

FIG. 8A shows a partial perspective and cross-sectional view of a thirdalternate embodiment of a catheter in accordance with the principles ofthe present invention;

FIG. 8B shows a view of the distal end of the catheter shown in FIG. 8A;

FIG. 8C shows a view of the distal end of the catheter shown in FIG. 8Ahaving an alternatively shaped secondary port;

FIG. 9A shows partial perspective and cross-sectional view of a fourthalternate embodiment of a catheter in accordance with the principles ofthe present invention; and

FIG. 9B shows a view of the distal end of the catheter shown in FIG. 9A.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to FIGS. 1-3, there is, generally illustrated by referencenumeral 20, a catheter in accordance with the principles of the presentinvention. As shown, catheter 20 includes an elongated flexible or rigidplastic tubular catheter body 22 having a proximal end 24 and a distalend 26. Catheter 20 includes proximate its longitudinal distal end 26 aphased array ultrasonic transducer 30 which is used to transmitultrasound and receive resultant echoes so as to provide a field of viewwithin which flow rates can be measured and features imaged. It isappreciated that the other types of ultrasonic transducers can be usedin the present invention, such as any mechanical types, or any dynamicarray types, for underblood operation within a field of ultrasound,especially in the cardiac chambers, through vessel walls, and withinlarge vessel, etc. An electrical conductor 32 is disposed in thecatheter body 22 for electrically connecting transducer 30 to controlcircuitry 34 external of catheter body 22. An access port 40 is disposedin catheter body 22 and extends from proximate the proximal end 24 ofcatheter body 22 to proximate the distal end 26 of catheter body 22.Access port 40 is configured to receive a therapeutic device, such as acatheter, medication, sensors, etc., so as to enable such items to bedelivered via access port 40 to distal end 26 of catheter body 22 foroperation within the ultrasonic transducer field of view. Such itemsmight be used for intervention; e.g., ablation catheter, surgicaldevice, etc., monitoring blood pressure, sampling blood, etc. A guidewire access port 42 is also disposed within catheter body 22 and extendsfrom proximate proximal end 24 of the catheter body 22 to proximatedistal end 26 of catheter body 22 for receiving a guide wire 44.

In the preferred embodiment of the present invention, the ultrasonictransducer preferably has a frequency of 5 to 20 megahertz (MHz) andmore preferably a frequency of 7 to 10 MHz. Intracardiac imaging in anadult will require image penetration of up to 2 to 10 centimeters (cm).In the preferred embodiment, catheter body 22 preferably has a diameterof 4 to 24 French one French divided by Pi equals one millimeter (mm)!and, more preferably, a diameter of 6 to 12 French. In the preferredembodiment, access port 40 has a diameter of 7 to 8 French and guidewire port 42 has a diameter of 0.025 to 0.038 inches.

As generally illustrated in FIG. 3, catheter 20 of the present inventioncan be utilized in a medical system including the appropriate controlcircuitry 34 for controlling operation of the ultrasonic transducer. Asillustrated in FIG. 3, control circuitry 34 is electricallyinterconnected to transceiver circuitry 35 (T/R) for receiving andtransmitting signals via a cable 36 to ultrasonic transducer 30. Inturn, transceiver circuitry 35 is electrically interconnected to Dopplercircuitry 37 and an appropriate display device 38 for displayinghemodynamics or blood flow. In addition, transceiver circuitry 35 iselectrically interconnected to suitable imaging circuitry 39 which isinterconnected to a display 41 for displaying images.

During operation, control circuitry 34 might be designed to causeultrasonic transducer 30 to vibrate so as to cause an appropriateultrasound wave to project from proximate the distal end 26 of catheterbody 22. The ultrasound wave, represented by lines 50 in FIG. 2, willpropagate through the blood surrounding distal end 26 and a portion ofthe body structure. A portion of the ultrasound wave so transmitted willbe reflected back from both the moving red blood cells and the like andthe body structures to impinge upon transducer 30. An electrical signalis thereby generated and transmitted by the cable 36 to the input oftransceiver 35. A signal might then be transmitted to Doppler circuitry37 which will include conventional amplifying and filtering circuitrycommonly used in Doppler flow metering equipment. Doppler circuitry 37will analyze the Doppler shift between the transmitted frequency and thereceive frequency to thereby derive an output proportional to flow rate.This output may then be conveniently displayed at display 38 which mightbe a conventional display terminal. Accordingly, the user will be ableto obtain a readout of blood flow rates or hemodynamic information.

In order to obtain imaging information, control circuitry 34 willlikewise trigger ultrasonic transducer 30 via transceiver 35 to vibrateand produce an ultrasound wave. Once again, a portion of the wave orenergy will be reflected back to ultrasonic transducer 30 by the bodyfeatures. A corresponding signal will then be sent by cable 36 totransceiver circuitry 35. A corresponding signal is then sent to theimaging circuitry 39 which will analyze the incoming signal to provide,at display 41, which also might be a conventional display apparatus, animage of the body features.

This imaging can occur while a therapeutic or surgical device is beingused at distal end 26 of catheter 20 within the field of view providedby ultrasonic transducer 30. Accordingly, the user will be able tomonitor his/her actions and the result thereof.

As illustrated in FIG. 3, catheter body 22 might include proximate itsproximal end 24 a suitable mounting structure 52 to the access port 40.A therapeutic or surgical device structure 53 might be suitably attachedto structure 52 by suitable means, e.g., threaded, etc. As illustrated,an elongated cable-like member 54 will extend along access port 40 andslightly beyond distal end 26 of catheter body 22 wherein an operativeportion 56 of the surgical tool might be interconnected.

Additional detail of distal end 26 of catheter body 22 is illustrated inFIGS. 4A and 4B. As illustrated in FIGS. 4A and 4B, ultrasonictransducer 30 might include a piezo electric polymer, such aspolyvinylidenedifloride (PVDF) 60, which is bonded by an epoxy layer 62to a depression 64 approximate distal end 26. Although some detail isprovided with respect to an embodiment of an ultrasonic transducer whichmight be used, it will be appreciated that various types of transducershaving various configurations and orientations might be utilized inkeeping with the present invention.

As illustrated in FIGS. 4A and 4B, the operational portion 56 of thetherapeutic device is illustrated as generally being capable ofoperation in the field of view of ultrasonic transducer 30. Accordingly,it is possible for the user to monitor operation of the therapeuticdevice by use of the ultrasonic transducer. Moreover, it is possible forthe user to monitor the features of the body within the field of viewbefore, during and after interventional activity. It is appreciated thatthe other types of ultrasonic transducers can be used in the presentinvention, such as any mechanical types, or any dynamic array types,etc., for underblood operation within a field of ultrasound, especiallyin the cardiac chambers, through vessel walls, and within large vessel,etc., so that various forms of field of views, such as tomographic(slices), etc., can be provided in the present invention. In addition,it is appreciated that the orientations of the scan array on thecatheter can include side-view, end-view, multiview (two or more viewsthat are movable or imminently directional transducer referred to in theliterature as "omnidirectional"), etc.

FIG. 5A shows a partial cross-sectional view of a first alternativeembodiment 70 of the catheter apparatus. The catheter apparatus has anelongated flexible or rigid body 72 having a longitudinal axis and aproximal end 74 and a distal end 76. Disposed proximate a second side ofbody 72 is a port 78 extending through body 72 from proximate proximalend 74 to proximate distal end 76 of body 72. Port 78 is for receivingand delivering to distal end 76 of body 72 a working tool 84. Workingtool 84 shown in the Figures is illustrative only, others types of toolsnow known or later developed may also be delivered to distal end 76through port 78. Proximate a first side of body 72 is a guide wire port80 extending through body 72 from proximate proximal end 74 to proximatedistal end 76. Shown in guide port 80 is a guide wire 86.

Distal end 76 is disposed at an oblique angle to the longitudinal axisof body 72, the first side of body 72 extending further in the directionof the distal end than the second side of body 72. An ultrasonictransducer 82, having a first side and a second side, is disposed at anoblique angle to the longitudinal axis of body 72 approximatelycorresponding to the oblique angle of distal end 76 of body 72. Thefirst side of ultrasonic transducer 82 is disposed proximate the firstside of body 72 and the second side of transducer 82 is disposedproximate the second side of body 72. Extending from transducer 82 toproximate proximal end 74 of body 72 is an electrical conductor 83connecting transducer 82 to control circuitry external of catheter 70,as described with respect to catheter 20 above. Having transducer 82disposed on an oblique angle toward port 78 allows for easyvisualization of tools, such as tool 84, extending beyond distal end 76of body 72.

FIG. 5B shows a view of distal end 76 of body 72, showing guide wireport means 80, transducer 82, and port means 78.

FIG. 6A shows a partial cross-sectional view of a second alternativeembodiment of the catheter in accordance with the present invention,generally referred to as 88. Like first alternative embodiment 70,catheter 88 has an elongated flexible or rigid body 90 having a proximalend 92 and a distal end 94. Catheter 88 also has a port 96 extendingthrough body 90 from proximate proximal end 92 to proximate distal end94. Port 96 has a distal end 97 proximal distal end 94 of body 90.Distal end 97 of port 96 exits body 90 at an acute angle to a first sideof body 90 toward distal end 94. Port 96 is for receiving and deliveringto distal end 94 a working tool, such as working tool 84. Catheter 88also has a guide wire port 98 extending through body 90 from proximateproximal end 92 to proximate distal end 94. Guide wire port 98 is forreceiving a guide wire 86.

Also shown in FIG. 6A is a transducer 100 disposed to a first side ofbody 90 between distal end 94 and distal end 97 of port 96. Extendingfrom transducer 100 to proximate proximal end 92 of body 90 is anelectrical conductor 102 disposed in the catheter body 90 forelectrically connecting transducer 100 to control circuitry external ofthe catheter. With transducer 100 disposed to the first side of body 90and distal end 97 of port 96 exiting body 90 at an acute angle relativeto the first side of body 90 toward distal end 94, working toolsextending from distal end 97 of port 96 will be within the field of viewof transducer 100.

FIG. 6B shows a view of distal end 94 of catheter 88, as shown in FIG.6A.

FIG. 7A shows second alternative embodiment 88, as shown in FIG. 6A,except instead of having a guide wire port 98, this variation of thesecond alternative embodiment 88 has a deflection wire guidance system106 for manipulating distal end 94. FIG. 7B shows a view of distal end94 of the catheter shown in FIG. 7A.

FIG. 8A shows a third alternative embodiment 110 of the catheter inaccordance with the present invention. Third alternative embodiment 110has a body 112 having a distal end 114 and proximal end 116. Disposedproximate a first side of body 112 is a primary port 118 extendingthrough body 112 from proximate proximal end 116 to proximate distal end114. Primary port 118 has a distal end 119 proximate distal end 114 ofbody 112. Oppositely disposed from primary port 118, proximate a secondside of body 112 is a secondary port 120 extending through body 112 fromproximate proximal end 116 to proximate distal end 114. Secondary port120 has a distal end 121 proximate distal end 114 of body 112.

Mounted proximate distal end 114 of body 112 is a transducer 122.Extending from transducer 122 through body 112 to proximate proximal end116 is an electrical conductor for electrically connecting thetransducer 122 to control circuitry external of the catheter. Transducer122 is disposed between distal ends of primary and secondary ports 119and 121, respectively. With working ports 118 and 120 oppositelydisposed on either side of transducer 122, it is possible to conduct twosimultaneous applications, such as holding an object wit a first tooldisposed through one port and operating on the object held by the firsttool with a second tool disposed through the other port. A typicalworking tool 123 and working tool 84 are shown disposed with ports 118and 120.

Although third alternative embodiment 110 does not include a guide wireport means, a guide wire could be used in primary port 118 or secondaryport 120 to initially position catheter 110. Then the guide wire couldbe retracted from port 118 or 120 and a working tool introduced. FIG. 8Bshows a view of distal end 114 of catheter 110.

FIG. 8C shows a view of a distal end 124 of a catheter 126 substantiallylike catheter 110 shown in FIG. 8A and FIG. 8B, except that catheter 126has a primary port 128 having an arc-like shaped cross-section, ratherthan a circular shaped cross-section. Although a circular cross-sectionhas been shown in the Figures for the various ports described herein,the size and shape of the ports can be varied without departing from theprincipals of the present invention.

FIG. 9A shows a fourth alternative embodiment 130 of the catheter of thepresent invention. Catheter 130 is similar to catheter 70 shown in FIG.5A and FIG. 5B, except that a plurality of ports 132 are disposedproximate a second side of flexible body 131, rather than one port 78,as shown in FIG. 5A. With a plurality of ports, it is possible, forexample, to use a therapeutic tool through one port while simultaneouslysuctioning and removing debris through another port; or a therapeutictool can be used through one port while simultaneouslyelectrophysiologically monitoring, suctioning and/or biopsying through asecond port, third or fourth port.

The use of the catheter of the present invention is described withrespect to the preferred embodiment 20. It is understood that the use ofalternative embodiments 70, 88, 110, 126 and 130 is analogous. In use,the user would insert flexible catheter body 22 into the body via theappropriate vascular access to the desired location in the body, such asselected venous locations, heart chamber, etc. In one approach, a guidewire might be first inserted into place and then the catheter body fedalong the guide wire. The user might then insert a surgical device intothe body through access port 40 and feed the surgical device toproximate distal end 26 of catheter body 22. Prior to, during and afteroperation of the surgical device, the user might obtain both hemodynamicmeasurements and images from the ultrasonic transducer field of view. Byoperation of the surgical device within the field of view of transducer40, the user can monitor operation of the surgical device at all times.

I. Detailed Features of the Disclosed Catheters

A. Frequency agility Ultrasound frequency: Frequency agility refers tothe ability of a transducer to send and receive at various frequencies,most commonly 3, 5, and 7 MHz. It is also appreciated that a singlefrequency from a single transducer device can be sent and received. Ingeneral, higher frequencies are used to image fine detail of moreproximal or closely related objects while lower frequency transducersscan more remote objects with less detail. The proposed device optimallyuses a 5 to 20 mHz transducer with the most optimally applied frequencyof 7 to 10 mHz. The lower frequency used in the UIHC reflects the needto image larger objects such as the cardiac septa, valves, andextravascular anatomy.

B. Catheter size: Catheter diameters will generally be larger thanintravascular catheters and will range 4 to 24 French with the optimalcatheter diameter 6 to 12 French (French size=French divided by Pi plusmillimeter diameter).

C. Intervention: One primary function of this catheter system is toguide the logical and safe use of various a) ablation, b) laser, c)cutting, d) occluding, e) etc., catheter-based interventionalcardiovascular tools. The invention has the access port through whichother technologies (devices) can be passed. Once the interventional toolexits the catheter tip, it can be directed repeatedly and selectively tospecific site for controlled intervention.

D. Imaging: The invention is also an imaging system capable ofvisualizing intracardiac, intravascular, and extravascular structures.Because the transducer frequencies utilized are usually lower thanintravascular systems, the catheter 20 can see multiple cardiac cavitiesand visualize structures outside the vascular system. The imagingcapability is basically two-fold: 1) diagnostic and 2) application.

1. Diagnostic imaging: The catheter 20 can effectively performdiagnostic intracardiac and transvascular imaging. This application willmore than likely be performed just prior to an interventionalapplication. The intervention then will follow using the same cathetersystem and its unique delivery capability. Some examples of diagnosticimaging include 1) accurate visualization and measurement of anintracardiac defect, 2) characterization of valve orifice, 3)localization of a tumor and its connections, 4) etc. Extravasculardiagnoses would include

1) visualize pancreatic mass/pathology,

2) retroperitoneal pathology,

3) intracranial imaging, 4) recognition of perivascular pathology, and5) etc.

2. Application imaging refers to the use of the catheter and its imagingcapability to deliver and then apply another technology such as 1)occlusion device for closure of a septal defect, 2) ablation cathetersfor treatment of bypass tracts, 3) creation of a defect such as thatwith the blade septostomy catheter or laser-based catheter system, and4) directing of valvuloplasty, etc. By direct imaging of an application,such as ablation, the procedure will be able to be performed more safelyand repeatedly, and the result can be better assessed.

E. Hemodynamics: The catheter 20 is a truly combined ultrasound Dopplerand conventional hemodynamic catheter. There are Doppler catheters, andthere are catheters capable of imaging and measuring hemodynamicpressure. However, the catheter 20 is capable of Doppler hemodynamics(continuous and pulsed-wave Doppler) as well as high-fidelityhemodynamic pressure recording while simultaneously imaging the heartand blood vessel. The catheter 20 provides a combination of imaging,hemodynamic, and interventional delivery catheter.

II. Analogy with Other Existing Therapeutic Technologies

Like interventional peritoneoscopy, intracardiac ultrasound is capableof 1) imaging, 2) delivering a therapeutic device, and 3) obtainingsimultaneous hemodynamics which can be used to develop less invasivecardiac surgical techniques. This simultaneous use of one or moredevices within the heart or vascular tree opens up the potential todevelop less invasive surgical therapies. Examples would include 1)removal of a cardiac tumor by visually grasping the tumor with onedevice and visually cutting its attachment with a second device, thusallowing less invasive extraction of intracardiac mass lesions, 2)visually placing an electrophysiologic catheter on a bypass tract andthen with direct ultrasound visualization ablate the underlying tractwith the second device, 3) visually performing laser surgery such ascreating an intraatrial defect, vaporization of obstructing thrombussuch as is seen in pseudointimal occlusion of conduits, 4) visuallyremoving a foreign body from the heart or vascular tree, and 5)directing intravascular surgery from within a blood vessel or monitoringconcomitant hemodynamic changes.

III. Selected Applications Include the Following:

A. Radio frequency ablation: Presently a bypass tract is localized by anelectrophysiologic study which systematically maps the atrioventricularvalve annulus. Positioning of the ablation catheter is determined byx-ray fluoroscopy and certain electrical measurements which relate thedistance of the ablation catheter from a reference catheter. Thecatheter 20 will allow an operator to map the atrioventricular valveunder direct ultrasound visualization. Thus, increased accuracy ofcatheter placement, precision of the applied therapy, and immediateassessment of outcome would result.

The above ablation technique would be particularly applicable forright-sided bypass tracts (in and around the tricuspid valve annulus).This would be accomplished by placement of the catheter 20 through thesuperior vena cava above the tricuspid annulus.

For left-sided bypass tracts, the catheter 20 could be placed across theatrial septum under direct ultrasound visualization. The mitral annuluscould thus be mapped directly and the localized bypass tract preciselyablated under visual ultrasonic and hemodynamic direction. Complicationssuch as valve perforation, multiple imprecise applications of ablationenergy, and inadvertent ablation of normal conduction tissue would besubstantially reduced.

Ablation of bypass tracts would be an ideal utilization of the proposedultrasonic interventional catheter system.

B. Cardiac biopsy: In the era of safe cardiac biopsy, there is a needfor precision biopsy. Ultrasound direction of the biopsy device to anintracardiac tumor, avoidance of scar, and selective biopsy of suspecttissue are feasible with the catheter 20 device. One of the morefrequently life-threatening complications in the cardiac catheterizationlaboratory is catheter perforation of the heart. Such complications mostcommonly accompany cardiac biopsy, electrophysiologic cathetermanipulation, and valvuloplasty. Use of an intracardiac ultrasoundimaging, hemodynamics, and delivery catheter should substantiallyincrease or improve safety of these procedures.

C. Transvascular diagnoses: The catheter 20 will allow visualization ofperivascular and extravascular pathology. Transvascular or transorganimaging and localization of pathology out of the immediate vascular treewill result in a substantial step forward in the diagnosis and possibletreatment of difficult to reach pathology. The catheter 20 cannot onlydiagnose but guide a biopsy needle and therapeutic device to anextravascular lesion in question. The retroperitoneum, mediastinum, andbasal cerebrovascular pathology are logical areas of interest. Accuratecharacterization of various pathologies will be more feasible. Everyorgan has its own vascular system, and the proposed ultrasoundtransvascular system is an ideal tool to assess difficult to reach areasof the body. The vascular system is a conduit to each organ, and thecatheter 20 can be delivered to each organ. Characterization of theunderlying parenchyma and possible transvascular biopsy or treatmentwill ultimately be developed.

D. Ultrasound manipulation of therapeutic devices within the heart andblood vessels: The catheter 20 opens the potential not only to visualizebut to directly intervene with the same catheter system. There arenumerous intraoperative catheter-based systems which to date useconventional x-ray to accomplish their goal of placement and applicationof a specified therapy. There is a need for a device which can moreprecisely guide such catheter-based systems. It is too expensive andtechnically impractical to incorporate ultrasound into everycatheter-based technology. The catheter 20 has all the prerequisites ofan ideal imaging and interventional instrument and has the ability to 1)image, 2) obtain hemodynamics by multiple means (pressure dynamics andDoppler, 3) function as a diagnostic as well as therapeutic device, and4) accommodate other unique technologies which would enhance theapplication of both systems.

E. General applications: It is anticipated that intravascular,transvascular, and intracardiac devices could be delivered through theport means described above within or about the heart and blood vesselsof the body. The catheters described above, however, could also be usedin any echogenic tissue, such as liver, parenchyma, bile ducts, ureters,urinary bladder, and intracranial--i.e., any place in the body which isechogenic which would allow passage of a catheter for either diagnosticor therapeutic applications using ultrasound visualization.

F. Expanding applications of technologies: The catheter is a new andexciting innovation to invasive medicine. There are multiple other andyet-to-be-determined applications. However, the new concept describedopens the potential development of less expensive, more precise, andsafe intravascular and transvascular diagnostic and surgical devices.

IV. Summary

The catheter 20 is very much different from any conventional ultrasoundcatheter-based system. The catheter 20 incorporates image andhemodynamic capability as well as the ability to deliver other diversetechnologies to specified sites within the cardiovascular system (heartand blood vessels). The catheter 20 is seen as an ideal diagnostic andtherapeutic tool for future development. The proposed applicationsfoster greater preciseness, adaptability, and safety. Ultrasound permitsvisualization from within blood-filled spaces as well as throughblood-filled spaces into other water- or fluid-filled tissue. Thecatheter 20 will evolve into the ultimate interventional system.

FIG. 4A is an illustration showing one potential use of the ultrasoundimaging and hemodynamic catheter (UIHC). In this particular example, theUIHC is advanced from the superior vena cava to the tricuspid valveannulus. Simultaneously visualized in the annulus, electrophysiologicand ultimately and ablation procedure are performed. The ability todirectly visualize and direct therapeutic catheter devices highlightsonly one of the many applications of the UIHC.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. A catheter apparatus, comprising:an elongatedbody having proximal and distal ends; a linear phased-array ultrasonictransducer mounted proximate the distal end of the catheter body totransmit ultrasound and receive resultant echoes so as to provide afield of view within which flow rates can be measured and featuresimaged; and an electrical conductor disposed in the catheter body forelectrically connecting the transducer to control circuitry external ofthe catheter.
 2. The catheter apparatus according to claim 1, furthercomprising a guide wire port disposed in the catheter body and extendingfrom proximate the proximal end of the catheter body to proximate thedistal end of the catheter body for receiving a guide wire.
 3. Thecatheter apparatus according to claim 2, further comprising a deflectionwire guidance system.
 4. The catheter apparatus according to claim 1,wherein the ultrasonic transducer has a frequency of 5 to 20 MHz.
 5. Thecatheter apparatus according to claim 1, wherein the ultrasonictransducer has a frequency of 7 to 10 MHz.
 6. The catheter apparatusaccording to claim 1, wherein the catheter body has a diameter of 4 to24 French.
 7. The catheter apparatus according to claim 1, wherein thecatheter body has a diameter of 6 to 12 French.
 8. The catheterapparatus according to claim 1, wherein the catheter body has a diameterof 7 to 8 French.
 9. The catheter apparatus according to claim 1,wherein the linear phased-array transducer is a multiplane phased-arrayultrasound transducer.
 10. The catheter apparatus according to claim 1,wherein the transducer is mounted on one side of the elongated bodyproximate the distal end of the elongated body.
 11. The catheterapparatus according to claim 1, wherein the catheter is applicable whenthe distal end and a portion of the catheter body adjacent thereto aresurrounded by blood.
 12. A catheter apparatus, comprising:an elongated,flexible body having proximal and distal ends and first and secondsides, wherein the first side extends further in the direction of thedistal end of the catheter than the second side; a linear phased-arrayultrasonic transducer, the transducer being mounted on proximate thedistal end of the catheter body and proximate the first side of thecatheter body to transmit ultrasound and receive resultant echoes so asto provide a field of view within which flow rates can be measured andfeatures imaged; and an electrical conductor disposed in the catheterbody for electrically connecting the transducer to control circuitryexternal of the catheter.
 13. A medical system, comprising:a cathetercomprising: an elongated body having proximal and distal ends; a linearphased-array ultrasonic transducer mounted proximate the distal end ofthe catheter body to transmit ultrasound and receive resultant echoes soas to provide a field of view within which flow rates can be measuredand features imaged; guide wire port disposed in the catheter body andextending from proximate the proximal end of the catheter body toproximate the distal end of the catheter body for receiving a guidewire; an electrical conductor disposed in the catheter body forelectrically connecting the transducer to control circuitry external ofthe catheter; control circuitry means for controlling operation of theultrasonic transducer; and display means for displaying the flow ratesand the features imaged by the ultrasonic transducer.
 14. A methodsystem according to claim 13, wherein the transducer is mounted on oneside of the elongated body proximate the distal end.
 15. A method ofmonitoring cardiovascular function using a catheter, the methodcomprising:disposing a catheter in one of a blood vessel and a heart,the catheter comprising: an elongated body having proximal and distalends; a linear phased-array ultrasonic transducer mounted proximate thedistal end of the catheter body to transmit ultrasound and receiveresultant echoes so as to provide a field of view within which flowrates can be measured and features imaged; guide wire port disposed inthe catheter body and extending from proximate the proximal end of thecatheter body to proximate the distal end of the catheter body forreceiving a guide wire; an electrical conductor disposed in the catheterbody for electrically connecting the transducer to control circuitryexternal of the catheter; transmitting ultrasound from the transducer;receiving resultant echoes of the ultrasound using the transducer;analyzing the echoes to image features.
 16. The method according toclaim 15 further comprising analyzing the echoes with Doppler circuitryto provide hemodynamic information.
 17. A method system according toclaim 15, wherein the transducer is mounted on one side of the elongatedbody proximate the distal end.